The present invention is generally related to hypodermic syringes and more particularly to syringes that include a needle that is retractable after the intended use to substantially prevent inadvertent exposure to the needle and reuse of the syringe.
Hypodermic syringes are widely used in the medical arts for administering medicaments and for drawing body fluid samples. Generally, hypodermic syringes have a metal needle attached either fixedly or removably that has a sharpened distal point for penetrating vial stoppers or patient""s skin. The hypodermic syringes and needles have been used for many years with few problems reported when the vast numbers and needles being used are considered. More recently, with the recognition of viral diseases that are transmitted by body fluids and greater sensitivity of the need to protect health care workers from inadvertent contact with previously used needles (commonly referred to as xe2x80x9csharpsxe2x80x9d) as well as the need to reduce criminal misuse of improperly disposed of needles and syringes, syringes and needles that include provisions to prevent reuse have been developed.
Provisions intended to prevent reuse of needles and syringes include a variety of sharps collector systems that are widely used in health care facilities. Other developments include needle attachments that may be readily broken off by practitioners once the syringe has completed its intended use. A variety of shielding mechanisms has been developed; some of which are currently commercially available. While many of these developments have reduced the incidence of inadvertent exposure of healthcare workers to sharps, most of these devices can readily be overcome by an individual determined to obtain and misuse a hypodermic syringe and needle. As a result of this problem, further developments in the art of hypodermic syringes have resulted in syringes with needles that withdraw into the body of the syringe once their intended use is completed.
U.S. Pat. No. 4,838,869 discloses a retractable hypodermic needle configured for one-time use wherein the needle is spring loaded and automatically irretrievably retracted into the hypodermic syringe when the syringe plunger is fully depressed, whereby protrusions on the end of the plunger engage tabs holding the spring loaded needle to release the needle for retraction. A potential problem with the design disclosed in this patent is that many times a practitioner may draw and expel a fluid several times during preparation for administration of a medicament, with this design, the practitioner could inadvertently discharge the retraction mechanism. Further, the design would be very difficult to manufacture in large volumes.
U.S. Pat. No. 4,900,307 discloses a hypodermic needle with an enlarged hub that provides provisions for selectively withdrawing the needle into the hub once the syringe and needle have completed their intended usage. While this disclosed design does substantially eliminate the problem of premature discharge of the retraction mechanism, the enlarged hub has a considerable xe2x80x9cdead volumexe2x80x9d that would result in a significant undeliverable retention of the medicament. Additionally, although the needle is secured in the hub after discharge, the syringe itself is still fully functional after the hub with the needle inside is removed.
U.S. Pat. No. 4,994,034 discloses a hypodermic injection system with a retractable needle wherein the needle retracts within the interior cavity of a syringe plunger. The disclosed invention includes a cylindrical spring housing with resilient fingers which capture a coiled spring that biasly holds a needle holder against the retaining force of the resilient fingers. The plunger in this disclosure has a frangible end, which when engaging the resilient fingers under a pre-determined amount of force, dissociate the remaining inwardly-tapered shoulders to spread the resilient fingers, allowing the coiled spring to eject the needle and its holder into the interior cavity of the syringe plunger. A syringe manufactured using this disclosure would be complex and difficult to assemble. It is believed that no successful commercial product has been produced using this disclosure.
U.S. Pat. No. 5,019,044 discloses a safety hypodermic syringe with a hypodermic needle fixed connected to a holder plate and constantly supported by a spring for making axial movement. The holder plate is normally retained by a clamp at a ready position for injection. When the plunger of the syringe is pushed to the bottom of the barrel, the needle is released from the clamp and is pushed by the spring to drop and further follow a rubber plug to be squeezed into a chamber in the plunger. Again, no successful commercial product has resulted from this disclosure, which would be complex to manufacture and appears to have a considerable undeliverable dead volume.
Another example of a syringe with a retractable needle is disclosed in U.S. Pat. No. 5,053,010. The disclosed syringe retracts the needle into a hollow plunger when additional pressure is applied on the plunger after the contents of the syringe are expelled. The disclosed design incorporates a sliding elastomeric seal which displaces from its forward position to a retracted position, thereby allowing additional forward travel of the plunger to actuate the retraction mechanism. A problem reported with this design is that, because of the soft nature of the seal, the seal may be prematurely displaced during its use in an injection. Attempts to overcome this difficulty by increasing the stiffness of the sealing member could impair the seal integrity.
U.S. Pat. No. 5,180,369 discloses a self destructive syringe assembly having a needle cannula fixed to a slidable piston. The slidable piston and slidable piston flange are held within the barrel of the syringe assembly by a compressed spring, a guide tube and a shatter ring. The plunger of the syringe assembly is a hollow elongated tube with a thumb flat at one end, a sliding gasket, a plunger shatter plate and a hook rim at the other end. The patent reports that when medicament is injected, the elongated hollow plunger is further thrust into the shatter ring, the shatter ring shatters, further allowing the slidable piston and slidable piston flange to thrust into the plunger shatter plate to shatter. The shattering of the plunger shatter plate causes the slidable piston and needle cannula to be thrust into the hollow plunger by the spring and is thus prevented from re-entering the guide tube. Again, no successful commercial product has resulted from this disclosure.
U.S. Pat. No. 5,180,370 discloses a syringe which has an internal mechanism for retracting the needle into the syringe after the injection has been given. In one disclosed embodiment, the needle is manually retracted by pulling back on the plunger, and in another, the needle is propelled by a compressed spring into a hollow chamber within the plunger. A syringe produced with this disclosure would be complex to manufacture, and no successful commercial product has resulted from this disclosure.
U.S. Pat. No. 5,188,599 discloses a hypodermic injection system with a needle that retracts within an interior cavity of the syringe plunger. The needle when retracted is held within the plunger. The disclosed device includes a cylindrical spring housing that has resilient fingers which capture a spring under bias holding a needle holder against the retaining force of resilient fingers. The plunger has a frangible end which dissociates when the outwardly tapered shoulders spread the resilient fingers, allowing the coiled spring to eject the needle and its holder into the interior cavity of the syringe plunger. The patent also discloses a body fluid sampling device that includes a double-ended needle for communication with an evacuated blood collection tube. This patent also includes a review of several earlier disclosures related to retractable needles. Attempts have been made to produce commercial products based on the disclosures of this patent, but as yet there is no successful commercial product.
U.S. Pat. No. 5,201,710 discloses a syringe fitted with a clamping device for the needle and with a mechanism to enable the needle to be automatically retractable into the syringe body at the end of an injection. The disclosed device includes inner and outer cylinders, openings at the ends of the outer cylinder, a third opening at an end of the inner cylinder and a closure for the third opening. The disclosed device further includes a needle with a head, a seal, a first spring to push the needle against the closure and a clamping device loaded by a second spring to maintain outward to the syringe and to release the needle. There is a diaphragm in the closure that bends before breaking and a sharp element to break the diaphragm. There also is a closure to prevent the needle from being accessible and a stop to prevent the second cylinder from being moved outwardly after the syringe is used. As is apparent from the description, the device disclosed by this patent is complex and would be difficult to assemble. No successful commercial product has resulted from the disclosure in this patent.
U.S. Pat. No. 5,385,551 discloses a non-reusable medical device that has a needle which is retractable by depression a plunger slidably mounted in the device. The disclosed device includes a front-mounted retraction mechanism that has a needle holder connected to the needle. The needle holder is supported along the axis of the device by a frictionally engaged retainer ring member coupled to the needle holder along an axially aligned sliding interface. The needle holder and retainer are positioned in the front portion of a hollow body. The front of a movable member or plunger presses against the retainer member passing around the needle holder which cannot move forward, thereby separating the retainer from the needle holder. The separation occurs by gradually reducing the extent of the sliding interface area until the retainer member pops loose from the needle holder whereupon the needle holder and needle are retracted into a cavity in the plunger in response to a retraction force applied to the needle holder by a previously compressed spring. Again, the device disclosed in this patent is complex, difficult to manufacture and appears to have significant undeliverable dead volume. Attempts have been made to commercialize products from this disclosure with only limited success.
U.S. Pat. No. 5,407,436 discloses a hypodermic syringe that has a hollow needle that is automatically retractable after use. The disclosed syringe includes a one-piece body molding that has a main chamber for a plunger, sample container or drug cartridge, a forward chamber to house a spring to bias a needle holder, and internal latching formations to retain the needle holder with the spring compressed in the forward chamber until automatic retraction when the latching formations are released by end of plunger movement. The patent discloses that the sealing between the plunger and the body is accomplished by an over-sized plunger head that forces head and wall deformation. The disclosed spring has seals at both ends for the forward chamber. The patent teaches that the needle, its holder, spring and seals can be installed using a sliding guide. In using a syringe produced using this disclosure, the practitioner would need to exercise care when drawing and expelling a fluid during filling, because the retraction of the needle is activated by depressing the plunger sufficiently to engage cooperating latches. The engagement occurs at the bottom of the stroke to expel fluid from the syringe.
U.S. Pat. No. 5,769,822 discloses a non-reusable syringe with a hollow plunger that has a seal member thereon. The position of the plunger and the seal relative to the barrel permits the plunger, with sufficient strength, to carry applied pressure through the device during injection of a fluid and yet permit the seal disposed at one end of the plunger to have maximum sealing integrity between the plunger and a cylindrical barrel disposed around the exterior of the plunger to abate leakage of the liquid in a chamber within the barrel, as the plunger is manipulated from an expanded position to and expended position and thereafter to a third or collapsed position.
U.S. Pat. No. 6,010,486 discloses a retracting needle syringe that substantially prevents reuse of the syringe by destroying the plunger rod and the needle hub and additionally, retracts the needle into the plunger rod. The disclosed syringe includes provisions that upon fully depressing the plunger rod and applying distally directed axial force, a frangible portion of the inner hub is broken and the plunger tip dislodges to allow a spring to urge a cutter to open the chamber inside the plunger.
Most of the devices discussed in the above referenced disclosures are somewhat complex, and many require manufacture and assembly of parts with potentially difficult assembly or tight tolerance requirements. Many of the designs depend upon a careful application of forces by the practitioner to draw and expel fluids from the syringe. Also, if the tolerances between the multiple components of the device are not carefully adhered to during manufacture and assembly, normal usage may result in premature activation of the retraction function of the syringe. Current conventional syringes are considered by users to be virtually fault-free and reliable. They are used for a variety of different procedures involving both xe2x80x9cone-shotxe2x80x9d fill and inject procedures, as well as more complex mixing measuring and delivery functions. In order for a retractable syringe to displace these functional, utilitarian and reliable conventional syringes, the retractable syringe should not significantly interfere with the users current practices, it needs to be substantially reliable and their cost should not be prohibitive. Current conventional syringes are often manufactured at rates of several hundred per minute and their cost is generally not a significant factor in their usage. Additionally every year, hundreds of millions of small capacity (one milliliter) syringes are used outside of the normal controlled health care environment by diabetics and other self-injectors who must daily accurately inject small amounts, often only a few tenths of a milliliter. These small capacity syringes are physically quite small, with an overall length of less than five inches and an inside bore diameter of less than one-quarter inch. Reviewing the disclosures above, one skilled in the art of high volume manufacturing recognizes that assembling hundreds of millions of most of these relatively complex devices with their retraction elements contained in such a small space as a one-quarter inch diameter bore is a daunting task. Additionally, many of the disclosed devices have substantial undeliverable xe2x80x9cdead volumesxe2x80x9d that substantially confound many diabetics"" need for accurate measuring, mixing of more than one type of insulin in the syringe and delivering small doses of insulin. The need thus exists for a selectively retractable syringe that is compatible with a small capacity syringe, that is capable of being manufactured at high volumes and is sufficiently non-complex to be reliable in use when produced at volumes of hundreds of millions per year. Such a device is disclosed herein below.
A hypodermic syringe with a selectively retractable needle of the present invention includes an elongate barrel with an open proximal end and a distal end defining a receiver having a distal inward shoulder. The barrel has a hollow bore therethrough extending from the proximal end to the distal end. The syringe has an elongate plunger having a proximal end, a distal end and an inner rod extending a distance distally from the proximal end. The plunger includes a hollow sleeve having a proximal end and a distal end, that is sized to fit slidably, extend beyond and disposed over the inner rod. The plunger also includes a hollow cutter extending distally from the inner rod to a distal cutting surface within the hollow sleeve, and a stopper disposed over the distal end of the hollow sleeve to cover the cutting surface. The stopper is sized to fit slidably within the hollow bore of the barrel to define a chamber to draw and expel fluid. The plunger further includes a displaceable collar that substantially prevents a movement of the inner rod with respect to the hollow sleeve, the collar being displaced by application of a distal force, greater than a force required to expel fluid from the chamber in the barrel, to the plunger. The collar is displaced by engagement with the proximal end of the barrel, and, when the collar is displaced, movement of the inner rod having the cutter attached thereto with respect to the hollow sleeve is allowed, and causes the cutting surface to cut through the stopper. The syringe further includes an elongate hub with a passageway therethrough and a stem with a proximal flange and an engagement. The stem is disposed within and sized for slidable movement within the receiver at the distal end of the barrel. The flange on the hub has a distal surface and a proximal surface defining a distal end of the chamber in the barrel. There is a clip having a proximal foot with an opening therethrough and a distal grip disposed on the stem of the hub. The proximal foot of the clip is disposed at the distal surface of the flange and the grip at the engagement on the stem. The syringe includes an elongate needle having a fluid path therethrough, a pointed distal end and a proximal end mounted in the passageway of the hub so that the pointed end of the needle extends distally outwardly and the fluid path of the needle is in fluid communication with the chamber of the barrel. There is an elongate spring disposed about the stem of the hub compressed between the receiver and the distal grip of the clip to provide a bias, so that when sufficient distal force, greater than the force needed to expel fluid from the chamber, is applied to the plunger to cause the cutting surface to cut through the stopper, the cutting surface then engages the flange and cuts through the flange to engage the clip and to cause the clip to release the engagement on the stem. The release allows the bias of the spring to urge a sufficient movement of the hub to a position within the syringe where inadvertent contact with the pointed distal end of the needle is substantially prevented.
The syringe of the invention has an undeliverable xe2x80x9cdead-spacexe2x80x9d volume substantially similar to conventional syringes, i.e., substantially no undeliverable volume. The syringe of the invention is as suitable for use in drawing, measuring, mixing and delivering small volumes of medicaments as conventional syringes. Unlike many of the devices disclosed above, the syringe of the invention is substantially unlikely to be inadvertently retracted by a user following currently used practices and procedures. The syringe of the invention does not depend on a user having to exercise substantially more care than with a conventional syringe when drawing and mixing fluids in the syringe to avoid inadvertent activation, and importantly, the syringe of the invention is compatible with the efficiency of high volume automated manufacture that utilizes much existing manufacturing equipment. Once needle is retracted in the syringe of the invention, the syringe cannot be restored to functionality, as the hub flange is cut through and the stopper is cut through rendering the syringe substantially unusable and protecting the needle point from inadvertent contact by anyone.